This invention relates to an improved cutting assembly in the form of a rotary head for a rotary lawn edger, trimmer or the like, and more particularly relates to improved methods and apparatus for cutting vegetation with a flexible non-metallic cord member.
It is well known to cut grass, weeds and other vegetation with a moving flail-like member, and it is now well known to employ a flexible non-metallic cord member for the purpose of cutting vegetation located in places which are inaccessible to apparatus employing a rigid steel blade. In particular, the trimmer which is marketed in various forms under the trademark WEED EATER, and which is described in U.S. Pat. Nos. 3,708,967; 3,826,068; and 3,859,776, is now widely known and used for this purpose.
This invention relates to an improved cutting assembly in the form of a rotary head for a rotary edger, trimmer or the like. The preferred embodiment is in the form of a portable edging and trimming tool wherein the cutting element is safe in most uses and avoids the hazardous conditions created by prior art devices.
The prior art is prolix with attempts at solutions to provide a safe, efficient and simply constructed rotary head for rotary edgers, trimmers and the like. One attempt comprises a rotating metal bar or the like which is rotated at sufficient speeds to effect cutting of grass, weeds or the like. However, such bars create hazardous conditions in that when they strike certain objects they act upon those objects in a fashion to create and project dangerous missiles which may strike the operator or individuals in the area of work.
Various attempts have been made to overcome the aforesaid hazardous conditions created with rigid-type metal cutting blades of the prior art. Most of these attempts to overcome the problem involve the utilization of some type of flexible flail which will have sufficient resiliency so as not to propel objects which are struck at high velocities. Most of these resilient type cutting elements of the prior art suffer a disadvantage in that they are not safe and mere resiliency is not sufficient to insure that the dangerous conditions will not be created when rotation is effected at desired cutting speeds. Further, the prior art cutting elements are generally not provided with means for easy replaceability in the event of wearing out and are usually expensive to replace.
The result has been that most of the prior lawn and edging apparatus have been unsatisfactory because of the dangerous conditions created by the rotating head. As a consequence, most lawn edging and trimming around trees and the like, which would otherwise be damaged by the metal blades, must be done manually, which is both laborious and time consuming.
There is depicted and described in the following West German Petty or Gebrauchsmuster Pat. Nos. 6,919,841; 6,919,842; 6,919,843; 6,919,844; 6,938,265; 7,043,648 and No. 7,238,972, one or more embodiments of a lawn trimming device having a disc-like head member arranged to be rotated by an electric motor, and containing a spool which is housed therein in coaxial relationship to the shaft of the motor. A length of flexible non-metallic line is coiled about the spool, whereby its free traveling end extends generally peripherally from the spool and head, and whereby such free traveling end will be swung arcuately about upon actuation of the motor to cut adjacent vegetation in the manner of a flail.
The German Device will cut effectively only light-weight vegetation and suffers severely from a high-breakage rate of the plastic line.
These disadvantages of the prior art, and especially the aforementioned German device, are overcome with the present invention, and commercially acceptable embodiments of a vegetation cutter and the like are herein provided, which are not only fully capable of cutting vegetation under most operating conditions, but which are also fully capable of other tasks completely beyond the capabilities of the German device, such as cleaning dead leaves, trash and other such debris from along fences, walls and the trunks or stems of trees and bushes. More particularly, however, the embodiments of the present invention are capable of operation with a much higher efficiency and much lower breakage rate of their cutting string than has heretofore been possible with prior art devices.
Contrary to presupposition, a plastic string can usually cut vegetation almost indefinitely without breaking, provided the string engages only vegetation of the type sought to be cut. On the other hand, it will also be apparent that if a plastic string does impact against a resistive object, such as a concrete wall or chain link fence or the like, the string or line will be more likely to break than will a rigid steel blade. Since this type of cutter is expressly intended to be used to cut vegetation adjacent such resistive objects, it will not be surprising that the string or line will often experience breakage, and that the string or line must therefore be replaced from time-to-time.
As shown in the aforementioned United States patents, it has been found necessary and desirable to provide trimmers with a spool having a substantial length of cutting line coiled therein, and to employ only a short unwound portion of the line as the cutting member. Thus, if a portion of the extended cutting portion of the line becomes damaged or broken, the cutting member may be replaced by manually unwinding a new portion of line from the spool, and extending this unwound portion to form the new cutting member.
This manner of manually providing replacement cutting line has been found to be subject to certain problems, however. As may be seen in the aforementioned U.S. patents, it is desirable to protect the coiled portion of the line from moisture and debris by enclosing it in a circular head member, and to extend the unwound portion through a peripheral aperture in this head member to form the cutting member. Therefore, if the string breaks at a point at or within the head member, it is often necessary to remove and disassemble the head member in order to gain access to the head member.
Another problem with providing for manually unwinding cutting line from its spool arises from the fact that the spool is recessed snugly within the circular head member to prevent the line from escaping from the spool and head member during revolvement of the spool and head member. Thus, when it is desired to withdraw or unwind more cutting string, it is necessary to draw the string about the edge of the flange of the spool, while the string is wedged between the rim of the flange and the surface of the housing, and this tends to damage the cutting line or string. Either that, or else it is necessary to bend the flange away from the head to provide more clearance from the cutting line, which tends to damage the spool. In either case, it will be apparent that this, in turn tends to greatly reduce the overall convenience of this type of cutting apparatus, and to create an operating problem which is not present in more conventional cutters.
It has been proposed to overcome this and other related disadvantages by providing such equipment with means for mechanically extending or feeding out lengths of cutting line from the head member. There is, for example, depicted and described in U.S. Pat. No. 3,928,911, issued to Pittinger, a mechanical line feeding mechanism for use with an apparatus for cutting vegetation and the like with a flexible non-metallic string. There is also depicted and described in U.S. Pat. No. 3,664,102, issued to Reber, a flexible non-metallic cord type trimmer which utilizes a mechanical line feeding mechanism.
Although the Pittinger device does provide mechanical and incremental line feed when actuated, the device is subject to certain disadvantages to limit its practical value. Thus, the device requires a pair of pivoted toothed jaws which cam the line member therebetween. The camming action of the teeth on the line member injures the line member and produces weaknesses and flaws therein. Hence, the teeth of the camming jaws cause internal flaws and indentations in the line member which are highly undesirable since such flaws and indentations weaken the line and contribute to line breakage as the weakened and idented section is withdrawn and used as the flail portion of the cutting assembly. In contrast, the device of the present invention includes no direct contact of mechanical elements with the line member itself and thus, avoids any chance of damaging any of the stored portion thereof.
The Reber device includes a toothed control wheel that positively derives a toothed line reel with which it is intermeshed. While this system provides mechanical and incremental line feeding it is relatively complex in construction thus rendering manufacturing difficult. In addition, the system of intermeshing elements adds excessive weight to the cutting unit thus rendering it difficult to handle and causing serious problems in the maintenance of rotational balance of the cutting assembly. In contrast thereto, the device of the present invention is simple in construction and involves lightweight components.
These disadvantages of the prior art are overcome with the present invention, and commercially acceptable embodiments of a vegetation cutter and the like are herein provided which are not only fully capable of cutting vegetation under most operating conditions, but which are also fully capable of automatically, incrementally, and mechanically feeding cutting line from the cutting head during operation of the device without incurring damage to the cutting line or any other portion of the apparatus.